retyc/retyc-outlook-plugin repository overview

⁠Retyc for Outlook

Send large files securely from Outlook — end-to-end encrypted, GDPR-compliant.
Files are encrypted client-side in the task pane and replaced by a secure download link in your message body.

⁠ ⁠

⁠Features

• Drag-and-drop into the task pane — files never go through Outlook's attachment system, so they never traverse Exchange in cleartext
• End-to-end encryption — encryption happens client-side in the task pane via the Retyc SDK⁠ (age / X25519 hybrid post-quantum) before bytes leave the WebView2 process
• Passphrase support — required for recipients without a Retyc account, or for passphrase-only transfers without a recipient list (≥ 8 characters)
• OIDC Device Flow auth — log in with your Retyc account directly from Outlook
• Configurable transfer expiry — pick how long the transfer link stays alive, from the task pane Options
• Bilingual UI — auto-detects Outlook's display language; English / French bundled, switchable from the Account tab
• Clean emails — a Retyc download link is appended to the message body; recipients are written into Outlook's To field on confirm

⁠Requirements

• An Outlook client supporting Mailbox API 1.7+: Classic Outlook on Windows, new Outlook on Windows, Outlook on Mac, Outlook on the web
• A Retyc⁠ account

⁠Usage

⁠1. Log in

Click the Send via Retyc button in the compose ribbon to open the task pane, then click Log in with Retyc. A code and URL appear — open the URL in your browser, enter the code, and authenticate. You can pin the task pane (📌 in the pane's header) to keep it open across drafts.

⁠2. Send files via Retyc

In a compose window with the task pane open:

1. Drop files into the dropzone (or click to pick).
2. The recipient list mirrors Outlook's To / Cc / Bcc fields — edit them in Outlook and the pane stays in sync. Your own address is filtered out automatically.
3. Optionally toggle Use a passphrase in the Options panel (≥ 8 chars) — required if you have no recipients, or for recipients without a Retyc account.
4. Pick a transfer expiry from the same Options panel.
5. Click Encrypt & insert Retyc link — the pane uploads the encrypted bytes, writes the merged recipient list into Outlook's To field, and appends a Retyc download link to the message body.
6. Click Send in Outlook normally.

The Account tab shows your current quota (storage + transfers) and lets you switch the UI language.

⁠Development

⁠Prerequisites

• Node.js 24+ (declared in package.json engines and .nvmrc)
• The @retyc/sdk package (declared as a runtime dependency, fetched from the public npm registry)
• An Outlook account that supports Mailbox API 1.7+

⁠Setup

npm install
npm run build:dev      # vite development build
npm run build          # vite production build
npm run watch          # rebuild on file changes
npm run typecheck      # vue-tsc --noEmit
npm run lint           # eslint src
npm run start          # vite dev server (HTTPS, port 3000)
npm run dev:setup      # regenerate mkcert leaf cert + manifest.dev.xml (used by DEV_VM workflow)

⁠Sideloading the add-in

1. Run npm run start to serve the bundle over HTTPS at https://localhost:3000.
2. Sideload manifest.xml into Outlook:
   • Classic Outlook on Windows: ribbon Home → Get Add-ins → My add-ins → Add a custom add-in → Add from File, pick manifest.xml.
   • Outlook on the web / new Outlook on Windows / Mac: Settings → Mail → Customize actions → Get Add-ins → My add-ins → Add a custom add-in → From File.
   • Microsoft 365 admin (org-wide): Microsoft 365 admin center → Settings → Integrated apps → Upload custom apps.
3. Open a compose window — the Send via Retyc button appears in the ribbon (group label "Retyc"). Click it to open the task pane.

For development against a Windows VM (recommended for testing Classic Outlook desktop on Linux hosts), see DEV_VM.md⁠ — it covers the mkcert setup, the IP-rewritten manifest.dev.xml, and the sideload procedure.

⁠Production hosting

A multi-stage Dockerfile is provided. It builds the static bundle with Node 24 and serves it through nginx 1.30 alpine-slim (~13 MB image). Images are per-environment: the manifest baked in (manifest.xml) and the API URL (VITE_RETYC_API_URL, defaults to https://api.retyc.com) are resolved at build time. Build a separate image for each environment.

# Prod
docker build -t retyc-outlook-plugin:prod .

# Other environments — provide your own gitignored manifest, override the API URL at build time
cp manifest.<env>.xml manifest.xml
docker build \
  --build-arg VITE_RETYC_API_URL=https://api.<env>.example.com \
  -t retyc-outlook-plugin:<env> .

The / redirect is hardcoded to /taskpane.html (relative). Browsers hitting the bare-domain root land on the task pane directly — Outlook itself fetches /taskpane.html and never relies on the redirect.

CI/release workflows publish to ghcr.io/retyc/retyc-outlook-plugin (and Docker Hub retyc/retyc-outlook-plugin once the credentials block in _docker.yml is uncommented).

⁠Project structure

src/
  main.ts         # bootstrap (Buffer polyfill, lucide icons, i18n, Office.onReady → mount)
  App.vue         # auth gate + UTabs (Transfer / Account)
  components/     # LoginWall, TransferTab, AccountTab, DropZone (lazy-loaded .vue)
  composables/    # useAuth, useTransfer, useDropOverlay
  shared/         # constants, sdk-factory, storage, token-store, upload pipeline
  i18n.ts         # vue-i18n singleton + locale detection
  locales/        # en.ts, fr.ts message bundles
  assets/         # custom.css with the @theme block
public/           # PNG icons (XML manifest does not accept SVG)
scripts/          # dev-setup.js (regenerates mkcert leaf + manifest.dev.xml)
taskpane.html     # Vite HTML entry (kept at repo root)
manifest.xml      # Office Add-in XML manifest (Outlook MailApp, VersionOverrides V1_0 + V1_1)
manifest.dev.xml  # generated for VM sideload, gitignored
Dockerfile        # multi-stage build → nginx:1.30.0-alpine-slim, ~13 MB

⁠Architecture

The add-in declares a single runtime — the task pane — and does all its work there. Persistence is delegated to Office.context.roamingSettings (mailbox-scoped, syncs across devices) wrapped by a small abstraction that falls back to localStorage when the page is opened standalone in a browser.

Why no OnMessageSend interception? Office.js's event runtime is isolated from the compose runtime on Classic Outlook desktop — getAttachmentContentAsync returns empty content for attachments unless the draft has been saved to Exchange first. Forcing a saveAsync would push the unencrypted attachment to Exchange in cleartext, breaking the E2EE threat model. We sidestep the whole problem by never using Outlook's attachment system: files come from a dropzone in the task pane and go through file.arrayBuffer() → SDK encryption → upload.

Send-via-Retyc flow

User opens a compose window and pins/opens the Retyc task pane
  └─ User drops files into the task pane (HTML5 drag-drop or file picker)
  └─ User types recipients (textarea, comma/semicolon-separated)
  └─ User optionally types a passphrase (≥ 8 chars)
  └─ User clicks "Encrypt & insert Retyc link"
       ├─ Read each File via file.arrayBuffer() — bytes stay in the WebView2 process
       ├─ @retyc/sdk encrypts client-side (age / X25519 hybrid PQ)
       ├─ SDK uploads encrypted chunks to the Retyc API
       ├─ item.to.setAsync(recipients) — only if recipients were provided
       └─ body.setAsync(existingHtml + retycLinkSnippet)
  └─ User clicks Send in Outlook → email goes through Exchange with no attachments,
     just the Retyc link in the body

⁠License

MIT⁠ — © Retyc / TripleStack SAS